Converting From Drive by Wire Throttle to Manual Throttle

Maybe I'm speaking over my head, but my initial thought is that it really isn't possible. Well, might be possible, but a HUGE effort. And I mean GALACTIC. The ECM controls the PCM and the other controllers in the vehicle with the various CANs in the vehicle and I think they are all integrated- meaning that you've have to disable or bypass darn near every system in the vehicle. You'd have trouble codes out the wazoo, drivability would be suspect until after you resolved a slew of stuff, and then probably only get nominal results.

Back in my auto crossing days there was a thing called a Tec 3 I think that was a fuel management system that was fully programmable that might do something like this, but that was taking a less sophisticated system and making it more so, not the other way around.

Bottom line, if you wanna get away from the nannies, you'd probably need to go back to a TJ at a minimum. Now I could be wrong and there might be a system on the market, but again, think would be a monumental effort and far from plug and play.

Longtallsally said:

Maybe I'm speaking over my head, but my initial thought is that it really isn't possible. Well, might be possible, but a HUGE effort.

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I'm not exactly sure it would be as bad as you make it out to be... but it would require some rather specialized fabrication.

You'd leave the TPPS and TPS both in place. You'd have to find some way to allow the ECU-actuated throttle to stay in place, while allowing a static override based on the cable. Then I'd assume every time the ECU tries to put the throttle in a different position than the cable is putting it, the CEL would illuminate and tell you that your TPS or TPPS or both plus likely at least one or two other things were bad. So you'd have to live with a near constant check engine light, and come inspection time, it'd be tough.

You'd likely get slightly worse gas mileage if you drove with your foot on the floor all the time, but I think it'd be a very small difference. And of course the ESC would be at least partially hobbled.. it would not be able to reduce throttle in order to stop wheel spin etc.

I have considered this in concept but my Jeep only has about 1800 miles on it. Once it's out of warranty in about three years I might seriously consider it, to the point of even cracking open the throttle body and potentially machining parts. But I think there's much better chances of making adjustments to the sensor positions to reduce or eliminate lag and that dead spot without having to resort to a cable operated system.

IMHO a throttle cable is the right way to do it but with ESC required for all new vehicles we are stuck with DBW from now on, or until the law changes, which is unlikely.

jedgerly said:

Has anyone ever attempted or successfully changed over to a manually operated throttle from the drive by wire throttle?

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The easiest way to do this would be a complete engine conversion to an engine/transmission and ECU combination that doesn't use DBW.

If you have a manual transmission, it may be technically possible to do the physical modifications for a cable-actuated throttle, then use an aftermarket ECU (like MegaSquirt) to control the engine. But that would be a massive project to get the custom ECU configured correctly. You'll also have tons of fun trying to figure to how to integrate it with the stock electronics system so that the dashboard, etc, all still works. In this aspect, it would be similar to an LS V8 conversion.

If you have an automatic transmission, it's probably nearly impossible.

The stock powertrain control system is "torque-based". The position of the pedal is not simply converted electronically to a throttle blade position. It is interpreted as a desired amount of acceleration or torque at the axle, taking into consideration the current speed and likely other things. Then a crap-ton of calculations are done to finally decide what the throttle position, ignition timing, fuel ratio, etc., all need to be to produce the desired amount of acceleration. All those calculations depend on various properly-calibrated lookup tables so the computer can make accurate assumptions about how much torque the engine is producing right now, and what combination of throttle/fuel/spark/variable-valve-timing would produce the desired amount of torque.

During these calculations, multiple sub-systems (traction control, speed limiter, rev limiter, torque management for auto transmission shifting behavior, etc) all have the opportunity to "deny" the torque requested by the driver, and limit it in multiple ways. This all involves another metric crap ton of lookup tables that must be properly calibrated.

With the auto transmission, the transmission controller is integrated into this system also in terms of desired output torque at the axle and current road speed to decide what transmission gear is best right now.

So, no... you can't just slap a cable-actuated throttle body on the engine and expect anything to work.

This is what makes it so difficult for forced induction kit manufacturers to create custom tunes. Plus, Chrysler doesn't openly share details of how the system works, what lookup tables are involved, how the lookup tables affect things, etc.

Here's an intro to how a torque-based ECU works (specifically for the Dodge Viper, but generally relevant in concept for any torque-based DBY engine system): https://www.hptuners.com/help/vcm_editor_tuning_how_to_advanced_e78.htm